Telephone call transmitter



May l, 1945., 'I A, HUBBARD 2,375,109

TELEPHONE CALL TRANSMITTER v Filed March 17, 1943 3 Sheets-Sheet l sa l 355549' Ha F/G. 2

FA. HUBBARD ATTORNEY May 1 1945. F. A. HUBBARD 2,375,109

TELEPHONE CALI.;` TRANSMITTER Filed March 17, 1945 5 Sheets-Sheet 2 CoDE CONTACTS key REG/STER [s7- ND RELAYS y /NVE/vron F A.. H-UBBARD 1 T' fog/Vey MaY, 1945- A. HUBBAR'D 2,375,109

TELEPHONE CALL TRANSMITTER Filed March 17, V1943 5 Sheets-Sheet4 5 LINE! LINE 2 LINE MARC/NAL S /VVE/VTOR 5,/ FAHUBBARD A Trop/v5 v Patented May l, 1945 omiso stares retenir Zldtt FFECE 2,375,109 TELEPQHQNE CALL TRANSMITTER Francis A. Hubbard, Maplewood, N. J., assigner to Bell Telephone Laboratories, Incorporated, New York, N. Y., a corporation of New York Application March 17, 1943, Serial No. 479,417

8 Claims.

subscribers stations of a key-calling telephone system'.

Key-calling telephone systems have been devised primarily to provide facilities whereby direct telephone connections to frequently called lines may be completed by a calling subscriber by ie simple expedient of actuating keys individually assigned to the stations of a group of frequently called lines.

A key-calling system of this general character is disclosed in United States Patent 2,347,108 of April 18, 1944. In that system each of fteen lines to which the key-calling subscriber has direct access is selected by the actuation of a key which functions to transmit, over the subscribers line to a signal receiving point, a station `identifying signal characterized by two consecutively transmitted signal components. In order that signal responsive translating devices function properly to record the transmitted signal, it is essential that each signal component be applied to the line for a predetermined interval of time, and that a predetermined interval of time elapses between the transmission of the two components. In the aforementioned copending application means, in the nature of magnetically operated timed mercury contacts, are employed which function to Vinsure the application of each of the two signal conditions to the line for predetermined intervals of time, and to insure the clearance of the first signal condition before the second signal component is transmitted. The use of such devices insures the required time intervals without imposing on the calling subscriber any requirements as to the manner in which the signal control keys are to be actuated.

It is the object of the present invention to provide a telephone call transmitter of the type disclosed in the above-identified patent, and in which the required time intervals are obtained on a purely mechanical basis.

This object is attained by depending entirely upon the use of purely mechanical means in a telephone call transmitter which function, incident to the actuation of any of a group of station selecting keys, to start a complete cycle of events, beginning when the actuated key reaches the bottom of its stroke and completing itself without any further influence from the key. This cycle f embodies all three of the time intervals, each of predetermined duration, that are required in transmitting a two-part station identifying signal.

In particular, the call transmitter of this invention embodies a contact controlling mechanism in the nature of a rotatable shaft to which are xed, in spaced relation, a plurality of cams,

each pair of which is adapted to actuate a particular set of contact springs whose closure determines the character of the components of the station identifying signals. The cam shaft is spring coupled to a drive shaft, and during the depression of any of the keys of the transmitter,

is held against rotation while the drive shaft is rotated through an arc of ninety degrees to store energy in the coupling spring. When an actuated key is fully depressed the cam shaft is released and, under the action of the coupling spring, is rotated, under control of an escapement mechanism, through an arc of ninety degrees and then is automatically arrested. During the rotation of the cam shaft the cams carried thereby act to operate their corresponding sets of contact springs. The cams and associated contact springs are relatively disposed so that only previously selected cams are effective in operating their contact springs. The cam selection is obtainedby means of select fingers, one for each camwhich,

under the control of the transmitter keys, may be selectivelyl interposed between their corresponding cams and an associated set of contact springs so that when the cam shaft is rotated the selected 'cams .force the corresponding select iingerinto engagement with the contact springs causing the springs to operate. Each pair of cams which functions to control the operation of a particular set of contact springs comprises two adjacent identical toothed discs, the teeth of one being peripherally displaced with respect to the teeth of the other so that when the two cams of the same group, or the nrst cam of any. group together with the second cam of any other group are selected in response to the depression of a key and the cam shaft is rotated, contact spring operations are produced sequentially.

That is, when the two cams of the same group are selected, the corresponding contact springs are operated and released by the rst cam and then reoperated and released by the second cam, and when the first cam of one pair and the second cam of another pair are selected the contact springs controlled by the first cam are operated and released and then the contact springs controlled by'the'second cam are operated and released. The cam arrangement is such that the contact closures eiected thereby are sustained for predetermined intervals of time and the space of time elapsing between successive contact closures is of sufficient duration to permit the signal condition determined by the rst contact closure to clear itself before the second contact closure is produced. In this manner the necessary time intervals are assured.

The escapement mechanism functions to control the speed of rotation of the cam shaft when driven by the coupling spring. Near the bottom of the key stroke a non-linear spring, acted upon during the down-stroke of the key functions with a snap break through action which insures the full depression of the keys and functions to restore the actuated keysto normal after the lapse of an interval of time of suicient duration to allow both signal components to be transmitted.

Having described in a general manner the call transmitter of this invention, the features and operation thereof will now be set forth in the following detailed description made with reference to the accompanying drawings, in which:

Fig. 1 is a side elevation of a telephone set equipped with the lcall transmitter of this invention, with a part of the casing broken away and showing an end View of the key controlled operating mechanism of the transmitter;

Fig. 2 is a plan view taken along the line 2-2 of Fig. 1 looking in the direction of the arrows;

Fig. 3 is a fragmentary side view of the telephone setshown in Fig. 1 and illustrates the position of the transmitter operating mechanism when one of the actuating buttons, or keys is operated;

Figs. 4, 5, 6, 7, 8, S, and 9a are enlarged views of certain structural details ofthe transmitter. Fig. 4 shows the latching device which maintainsthe carri shaft stationary during the depression of the buttons or keys; Fig. 5 shows the escapement mechanism which controls the speed at which the cam shaft is rotated; Fig. 6 shows the Anormal relative positions of a set of signal determining contact springs, of the toothed cams used to operate the springs and of the select nger which serves to effectively associate the cams with their corresponding contact springs; and Figs. 7 and 8 show the operating mechanism which functions to rotate the drive shaft when any of the buttons or keys is operated. Fig. -7 shows the position of the mechanism prior to the actuation of a key or button and Fig. 8 shows the mechanism when the actuated key or button'has been fully depressed. Fig. 9 is an enlarged view of the spring coupling. Fig. 9a is an enlarged View of the non-linear restoring spring.

Fig. 10 is a schematic representation showing the six code bars and the manner in which they are actuated in combinations by each of the `fifteen station selecting buttons or keys;

Fig. 11 is a table showing the Contact combinations effected by each key and the register relays which operate in response to each particular contact combination;

Fig. 12 vis a circuit diagram of a key calling ltelephone system with which the key set or telephone call transmitter of this `invention functions; and

Fig. 13 is an end view of the structural elements shown in Fig. 9. n

Referring now to Figs. 1 to 9, inclusive, and Fig. 13 of the drawings the telephone subscribers telephone set consists of the usual handset support of the cradle type formed integrally with the casing 3 kand a base l formed withvertically extending flanges 1 by virtue of which the casing 3 is tted to the'base. .On the front face of the casing 3 is mounted the usual dial finger-wheel 5, fifteen manually depressible buttons KI to KI 5, inclusive, and a designation strip 43 located immediately below the buttons or keys. The strip 43 is transparent and embodies the designations corresponding to the keys or buttons in any suitable manner.

Each of the manually depressible keys or buttons Kl to KI5, inclusive, consists of a cylindrical portion protruding through an opening in the casing 3. Each button is provided with a angc 21 which abuts the inner surface of the front face of the casing 3, and of a lower cylindrical portion which protrudes through an aperture in the plate 28 which is secured to the underside of the dial cup 3l. Interposed between the lower face of flange 21 and the upper face of the plate 28 is a coil spring wound loosely about the lower cylindrical portion of the key. This spring functions to maintain the button in its normal position as shown in Fig. 1.

The buttons or keys control the operation of six code bars, ad. au, cd, cu, bd and bu which are substantially U-'shaped and are located at the forward end of the telephone set. The inwardly projecting portions of the U-shaped bars are apertured to accommodate the rods I6 and Il about which the bars are adapted -to be rotated. The rod I6 which may be a screw bolt accommodating the nut 24 is supported by two oppositely disposed ear-like extensions I8 formed integrally with a vertical extension i9 of a mounting plate 9 secured to the base I by screws I2. The rod I1 is supported in a similar manner by the ear-like extensions 20 of the vertical extension 22 of a mounting plate 6 and is threaded at one end to accommodate the nut 26.

Each U-bar is provided with an integrally formed inwardly projecting extension 32 which vhas xed to its inner end a hook-shaped select nger 34. Thus, there are six select iingers such asshown at 34 each individually and integrally associated with onerof the code bars through the extension 3?.. The elongated portions of the U- bars which extend across the front portion of the telephone set below the row of selecting buttons KI -to K l 5, inclusive,` are provided with` projections or fingers 23 located in various positions throughout the length of the bars. These extensions are so arranged that the bottom face of each button will engage one or more thereof when the button is depressed. Thus, when any button is depressed,'a certain number of the projections 23 Y will be engaged to cause a corresponding combination of code bars to be rotated about the pivot rods i8 and l1. The rotation of the U-bars in this manner causes the corresponding select fingers 33 to be moved upwardly for a purpose to be hereinafter described.

' Also supported between the ear-like appendages or lugs 20 for pivotal movement about the rod I1 is a common U-bar 45. This bar, as clearly shown in Fig 41, is located immediately below the inwardly projecting left arms of the six code bars so as' to be operated thereby when any of the code bars is actuated. The inner edge of the upper or right arm (viewing Fig. 2) of the common bar 45 normally rests against the center line of an elongated spring 93 which is supported on the mounting plate E by means of two brackets Ell. This spring has a non-linear characteristic and functions with a snap break through action when the bar 45 is actuated and serves to restore the bar 45 to its normal position. The purpose of this break through aotionof spring 93 will be set forth in detail hereinafter.

Three sets of contact springs A', B' and C (Fig. 2) are mounted on the mounting plate 6 so that each set is adapted to be engaged by two adjacent select fingers 34 as will appear from a later description. The two outer sets of contact springs A' and B' are identical and are of the transfer type comprising three springs 5|, 53 and 55 mounted on the plate 6 by means of screws 49,v

as shown in Fig. 6. Each spring carries a contact, and springs 55 and 53 function as break f springs while the springs 53 and 5| constitute make springs. The center set of contact springs C consists of only two springs similar to thev springs 5| and 53 of Fig. 6.

The contact control mechanism comprises a square sectioned drive shaft 40 and a cam shaft 38 each of which has an outer end passing through an aperture in a vertically extending lug 36 of the mounting pla-te 6. The cam shaft 38 carries siX identical toothed discsor cams 44, 48, 48, 50, 52 and 54 which are so disposed on the shaft 38 as to constitute three sets of cams each consisting of two toothed discs. which are in substantial alignment with the select ngers 34 of code bars ad and au respectively, constitute one group; cams 48 Iand 50, which are in substantial alignment with the select fingers 32 of code bars ed and cu, respectively, constitute a second group; and the cams 52 and 54, which are `in substantial alignment with the select fingers 32 of code bars bd and bu, respectively, constitute the third group. 'Ihe cams are normally` out of physical'engagement with the contact springs corresponding thereto, but when any of the code bars is actuated the corresponding select finger is moved upwardly so as to -be interposed between its corresponding cam and the corresponding set of contact springs, so that when the cam shaft is rotated, subsequent to the actuation of the code bars, the contact springs of the sets A', B vand C are operated in combinations corresponding to the combination of select fingers actuated. As shown in Fig. 6 the cams of each pair vof cams are identical toothed discs but are so peripherally displaced on the shaft 38 that the teeth of one are displaced forty-five degrees relative to the,

teeth of the other. Thus, when the shaft 38 is rotated one cam of a pair functions (if its corresponding select finger has been actuated) to operate the corresponding contact springs during one interval of the period of rotation of the shaft and the other cam functions (if its corresponding select finger has been actuated) to operate the contact springs during a succeeding interval of the period of rotation of the shaft. o

The cam shaft38 and square sectioned shaft ill are coupled together by means of a spiral spring 42, the opposite ends .of which are fixed respectively, to the cam 85 and ratchet 8|, the former fixed to shaft 38 and the latter to the square sectioned shaft 40; Thus the square sectioned shaft 40 functions through the spring 42 to drive the cam shaft 33 in a manner which will be described in greater detail hereinafter. As clearly shown in Fig. 9 the square sectioned shaft i8 is provided with an integral pin-like extension which fits into one end of shaft 38. This pin serves as a bearing for one end' of shaft 4U.

Near its upper or right end (viewing Fig. 2) the cam shaft 38 carries an escapeme-nt wheel Cams 44 and 46 any further rotation of the shaft.

period of rotation of shaft 38 the contact spring- 56 which cooperates with an escapement pawl 89 to control the speed of rotation of the shaft 38. The pawl 89 is pivotally supported between the two arms of a U-shaped bracket 30 xed to the plate B by screw 9| as shown in Fig. 5.

.The square sectioned drive shaft 40 is actuated in response to the operation of any of the keys or buttons KI to K5, inclusive, through the mechanism shown, particularly, in Figs. 7 andv 8. On one end of the shaft 48 is fixed a ratchet wheel having four teeth two of which are identified by the numerals. 'i8 and 95. The commonbar 45 is provided with an inwardly projecting arm 25 which pivotally carries at its end a pawl 51, which in turn, pivotally supports at its end a dog consisting of two arms' 6I and 'i4 which are disposed at right angles to each other. This dog is carried by the pivot pin 52. When'a key or button is depressed it actuates one (or more) of the code bars which acts (or act) upon the common bar 45 causing it to rotate about the rod and to raise the extension 25. The pawl 51 is accordingly lifted causing the dog end 6| to engage the ratchet tooth 18 and to rotate the square sectioned shaft through ninety degrees. The position of the ratchet and pawl after such operation is shown in Fig. 8. The ratchet is partially enclosed by twosheet spring elements joined at 'I2 and provided with a spring extension'lS which, by engagement with the dog end 14, serves to maintain the dog in Contact with the ratchet during the actuation of the pawl 5T. When the common bar 45 restores to normal the pawl 51 is lowered carrying the ydog with it so that the portion 6| thereof engages the next succeeding tooth95 of the ratchet inl preparation for a subsequent actuation of the transmitter.

During the rotation of the drive shaft 40 under the inuence of an actuated key or .button the coupling spring 42 is wound up since, during this interval it is unable to transmit the movement of the drive shaft 48 to the cam shaft'38 because' the latter is held against rotation by a latch 88, pivotally mounted on the bracketl 32, which normally engages one of four teeth of the ratchet 8| and is heldin engagement with the ratchet by the spring 84. The ratchet 8| is fixed to the cam shaft 38. The latch is provided with a pin 86 which is normally in engagement with a cam 85 fixed to the drive shaft 3B. When` the drive shaft is rotated with its cam 85 through an arc of substantially ninety degrees one of the camming teeth of the cam 85 acts upon the pin 88 to cause the latch 88 to be disengaged from the ratchet 8|. When this occurs the cam shaft 38 is released and is rotated under the influence of the spring 42. A pawl ||3 pivotally mounted on bracket l I0 is held in engagement with the square shaft 48 by means of spring H2. This pawl permits the shaft 40 to rotate in one direction when a key is actuated and precludes rotation thereof inthe reverse direction. When the cam 'shaft has rotated through an arc of ninety degrees the latch 8U engages the ,next succeeding tooth in the'ratchet 8| to prevent During this sets, A', B and C', are actuated in accordance with the combination of cams selected by the ac tuated selectflngers 34. The first earn of each group functions during a first interval of rotation of the shaft 38 while the second cam of each group functions during a subsequent inter- -val, the two intervals being spaced by a time interval during Which the contact springs operated during the first interval are restored to normal. f

As lr'ereinbefore indicated the non-linear spring'93 is' engaged by the common bar 45 whenever a key or button is actuated. As the depressed key nears the bottom of its stroke the spring 53 flexes with a snap which serves to insure the key being fully depressed. The nonlinear spring 93 associated with the common bar 45 in exing with a snap, provides a break through key action which is assisted by the sudden release of the pavvl, or latch 8|] to throw the actuated key all the way down. With this breakthrough key action the need for a latching mechanism for insuring that the select finger, or fingers remain in operative `position until engaged by the cams is precluded since it requires a certain amount of time to reverse the motion of the ngers. depressed key the spring 93 functions to restore the common bar 45 and the actuated code bar or bars.

It will be observed that any partial actuation of a key or button will not result in the operation of any contact springs. This is due to the fact that the contact controllingmechanism, cam shaft 38, cannot operate until the latch 80 is disengaged from the ratchet BI and this does not occur until the cam 85 has been rotated through substantially ninety degrees and acts upon pin 86 to raise the latch.

The following description is directed to the operation of the call transmitter of this invention and for this purpose it Will be assumed that the key Kl is depressed. `When I the key Kl is depressed code bars ad and bu are actuated in accordance Wih the showing in Fig. 10, by virtue of the engagement of the lowerface of the key with the projections 23 extending from the code bars ad and bu, The select ngers 34 integrally associated With the extensions 32 of the actuated code bars are accordingly raised so as to be interposed between springs 53 of the contact sets A' and B' and their corresponding cams44 and 54. At the -of ninety degrees, The coupling spring 42 is accordingly Wound up sincev the cam shaft 38, at this time, is held against rotation by the latch 80 and its engagement with the ratchet 8|. Thusenergy to drive the cam shaft is stored in the spring 42. When the drive shaft is rotated-almost ninety degrees the cam 85 fixed thereto trips the latch 83 thereby releasing the cam shaft 38. The shaft 38 thus rotates under the action of spring 42 at a rate of speed determined by the escapement mechanism. During the rotation of the cam shaft 38, a tooth of cam 44, through its corresponding select finger 34 actuates the contact springs A causing the spring, such as spring 53 to move out of engagement with the spring, such as spring 55 and into engagement with a spring such asv spring 5|. When the tooth of cam 44 rides off its corresponding select linger 34 the set A of contact springs resumes its normal unoperated position. The tooth of cam 54 then becomes effective to operate the spring contact set B through its corresponding select finger and when this tooth rides off the select nger the contact springs resume their normal positions. It Will be` observed that this sequence of contact spring operations is start- When the subscriber releases the ed when. the latch 80 is disengaged from the ratchet 8|, that is when theactuated key KI has been fully depressed and is completed independently of any further iniiuence of the actuated key. When the shaft 38 has been rotated through ninetydegrees the latch 80 functions to arrest any further movement thereof, It will also be ob-` served that the actuated common bar 45 and code bars ad and bu are restored to normal under the influence of spring 93. While the coil spring 28 will function to restore the actuated keyKlA to normal it will be' noted that this spring may be omitted if desired since the restoration of the actuated code bars by the spring 93 will also cause the key KI to return to normal because of the enf gagement of the code bar projections 23 therewith.

The following description is directed to the operation of the subscribers telephone call transmitter in connection with a telephone call originated at the substation X and intended for a station on line No. 1 indicated at the right of Fig. 12.

Before entering into a detailed description of the operation of the system disclosed it may be well to refer briefly 'tothe subscribers substation cirsuit illustrated and also to the signal-receiving circuit. The subscribers telephone equipment per se, is indicated schematically at X and aside from the regular transmitter, receiver and auxiliary cir cuit equipment, the subscribers set includes two oppositely poled rectiers of the dry. disc type. These varistors or rectifiersare indicated at |00 and ||J|. A resistance |82 is also provided for a purpose which will be indicated presently, The svvitch elements |33 and |04 are serially included in one of the line Wires extending from the substation X and when operated serve, first to open the line conductor to the'station and then to effectively connect their associated rectiers across the line. The contact element |04 corresponds to a contact spring, such as spring 53 of Fig. 6 and its back contact I 0'! and its front contact A correspond respectively to the contacts associated with springs such as springs 55 and 5| of Fig. 6. 'Ihe contact element |03 and its associated back and front contacts correspond respectively to a contact spring such as spring 53 of Fig. 6 and the contacts of springs such as 55 and 5| of Fig. 6 which, actually constitute the spring set B shown in Fig 2'. The switch |||l controlling the resistance |02 is a simple make contact spring arrangement and corresponds to thevcontact set C shown in Fig. 2.

The signal receiving circuit comprises essentially relays H9, ||8,.|23 and |3I. Relay ||8 is a marginal relay connected in a full Wave rectifier bridge circuit and Will operate on current of either positive or negative polarity if of sucient amplitude. The neutral relays |23 and |3| Will operate only on positive and negative current, respectively. Relays |23 and |3| are substantially more sensitive than relay V| |8. The register relays I',

2', 4' and 8 are operated by the contacts of relays |23 and Htl,l and are locking. A progress relay chain, comprising relays |33 and |34, transfers contacts of relays |23 and 8 from register relays and 8' to relaysZ and 4 when the signal component transmitted during the first signaling interval has been recorded. Relay ||9 has a speed characteristic such that it Will hold up on alternating current, but will release and not reoperate when one half Wave is suppressed by either of the rectifiers at the substation. In its operated position it disables relays |23, |3| and ||8,

To initiate a call to a particular station the subscriber at station X actuates the key button assigned to the particular called station after having removed the telephone handset from its support. It will be assumed for descriptive purposes that the called station is located `on line No. 1 and thatthe key button assigned to .this station is key button KI. It will be observed from an inspection of the table shown in Fig. 11 that when key Kl is actuated contact A is first made followed by the making of contact C. In a previous description it was pointed out that when key Kl was actuated the lcontact set A of Fig. 2 was first actuated by cam 44 and then the contact set B was actuated by cam 54. Thus when key Kl is actuated contact A of the set A is closed to connect rectifier across the line in series with resistance |02 and contact B is subsequently closed to connect rectifier |00 across the line in series with resistance `|02 and each time `a rectiiier such as |0| or |00 is connected across the line, the line conductor to the station X is ,opened at the back contacts |01 and |05, respectively.

When the handset at station X was removed from its support and prior to the actuation of key K|, relay ||9 operated on the full Ywave rectified current, from' source H6, traversing the line, and at its right armature opened the circuit to relay ||8 and at its left armature short-ciri cuited relays |23 and |3| and their associated rectiers. When the cam shaft 38 rotates after the key Kl is fully depressed as previously described, the cam 44- functions to operate the spring contact set A so that the station X is disconnected from the line at contact |07 and rectifier ||J| is connected to the line at contact A. With rectifier |0| connected across the line it suppresses the negative half of the wave and resistance |02 reduces the positive half of the wave to a value insuiiicient to operate relay ||8 but i great enough to operate relay |23, it being understood that when the next negative half cycle is applied to the circuit relay I9 releases to con` nect relay ||8 into thefull wave rectier circuit and to remove the shortfrom relays |23 and |3|. The operating circuit for relay |23 maybe traced from the upper terminal of the secondarywinding of transformer ||5 whose primary is connected across the alternating current source ||6, recti` l fier Il., winding of marginal relay H8, back con- Due to the inclusion the circuit traced. Relay ||9 though traversed i by the positive half wave does notv operate.

At its right armature and front contact, relay |23 ycompletes an operating circuit for relay |30 which may be tracedv from grounded battery, winding of relay |30, right armature andfront contact of relay |23, back contact and armature of relay `|3|, to ground; Register relay l nowv operates in a circuit extending from ground, left armature and front contact of relay |23, inner left armature and front contact of relay |30, innermost left armature and back contact of relay |33, winding of register relay I to grounded battery. Relay |34 of the chain relay circuit also operates in a circuit extending from grounded battery, winding of relay |34, front contact and outer right armature of Vrelay |30 to ground.

i cut-through relay 12|.

Relay |34 operated, establishes an obvious locking circuit for register relay l', which circuit includes the outermost armature and front con` tact of relay |34. Relay |34 locks -to ground associated with the outermost lower armature of Thus, as a consequence of the rotation of shaft SBjthrough the nrst portion of its operation during which cam 44 is ef-` ective,l relays |23, |30, |34 and operate, the

last two locking. i .i When the tooth of cam 44 rides o1`f its correspondingselect finger 34 the springs of contact spring set A' restore to normal whereupon relay I9 reoperates on the full wave rectified current. This disables relays |23, |3| and ||8 asherein.- before described. Relay |23released,icauses relay |3e to release its` armatures whereupon .the secondrelay |33 of `the relay chain operates in a circuit extending from grounded battery, winding of relay |33, front contact and middle armature of relay |34, back contact and outer arma-` ,ture or' relay |30 to ground. Relay |33 in operating, transfers the contacts of relays ,|23 and.

line and contact B is closed to connect rectifier.

lull across the line infseries with resistance |02. With rectifier lull connected across the line the positive half wave is suppressed and resistance iUZ limits the amplitude oi' the negative half wave to a value insufficient to operate relay i8.

Relay IIS releases and` on the ensuing negative half cycle relay |3| operates in a circuit extending from the lower terminal of the secondary of transformer |15, whirling of relay ISL-rectir'iers |40 and |25, back contact and middle lower armature of relay I2l, contacts |04 and |01, `contacts |03 and B, rectifier |00, resistance |02, inner upper armature and back contact of` relay vizi, rectifier |4|, winding of relay ||8, rightA armature and back contact of relay H3, rectifier |42, to the upper terminal of the secondary of `transformer ll. Relay H9, though traversed by this current does not operate.

Relay |3| operated, causes relay |30 to operate i H8 is operated at this time `no other register i relay operates. Hence register relay i alone responds to the actuation of key Kl, and functions to cause the extension of the calling `line to the called line to which key KI is individually. assigned, as will now be described.

With register relay operated and locked under control of relay |34, an operating circuit for line connecting relay |50 is prepared which extends from ground, armature and front contact of register relay I', first armature and back contact of register relay 2f, second armature and back contact ofregister relay 4,-fourth armature and back contact of register -relay 8', winding of line connecting relay |50, conductor |52 to the front contact associated with the outer upper armature'of relay |2|. Relay' llLhowever, does not Yoperate until cut-through relay |2| operates to supply battery to the circuit .iusttraced Relay |2| is slow to operate. When relay |30 operated subsequent to the operation of thesecond the outermost lower armature-of relay |2| are of the make-before-break variety so that ground is connectedto conductor |6I before it is disconnected from the conductor ivthereby insuring the completion ofa substitute locking circuit for register relay beforeA the locking circuit to relays 133 and i3d isopened, the latter of which relays, up to thisvtimamaintained relay I locked operated. Thus register relay l is held operated under control of relay |2| which relay also serves to complete the operating circuit for line connecting relay |563.v i

-At its inner upperand its vinnermost lower armatures and front contacts relay |2| extends the calling line L to the link LY which, in turn, is extended to the called lineNo. l by the operation of line connecting relay |50. The lower Wind-ing of relay itl is now included in the com'- pleted line connection and is thus held operated from battery and ground, |56 and |57, which are shown connected to the link L. 'Ihe operation of relay 12| also opens the signal Areceiving circuit including relays HS, H3, |23 and ISI. With the locking circuit for relays |33and |34 opened at the back contact and outermost lower armature of relay |2|,Ythese relays are restored to normal and with the exception of cut-through relay |2|,

register relay l and line connecting relay |50, all relays ofthe system disclosed are normal unoperatedcondition.

The table shown in Fig. 11 indicates the contact operations which result from the operation of each of thel keys Ki 4to Kif inclusive, of the subscribers telephone call transmitter and also the register relays which operate inresponse to these contact operations. It isbelieved unnecessary to describe theoperation of the system in response to the actuation of each of the station selecting keys.V However, a more complete description, contained in the above-identified patent, is applicable to the circuit disclosed in Fig. 12 of this application.

It will be observed that in the table of Fig. 1l the column headed Contacts is4 divided into tWo` smaller columns headed respectively 1st and 2nd It is to-be understood that the contacts listed in column lst are operated by such cams as cams lili, i8 and 52 during the first interval of the signal transmittingr period while the contacts listed in column 2nd are operated by such cams as cams 46, 58 and 54 during the second signal transmitting interval, and that the two intervals are time spaced by an interval corresponding to the time durngwhich the rst contacts operated` are released and before the second contacts are operated. Thus the contact in their controlling cam shaft functions to provide the three intervals required in the transmission of a signal comprising two consecutively transmitted signal components. f

It is to be noted also that the contact spring set C shown in Fig. 2, is operatedtogether with either the contact spring set A Yor the contact spring set B for certain keyoperations and that when thus operated the springsof the set C' function to effectively exclude the resistance |82 from the signaling circuit which, as fully described in the aforementionedpatent vapplication increases the amplitude of the unsuppressed half wave to a value sufficient to operate marginal relay H8.

What is claimed is:

1. In a call transmitter, the combination of a plurality of depressible keys, a plurality of sets of contact springs, a control mechanism for operating said sets of contact springs comprising a rotatable shaft, a pair of cams for each set of contact springs mounted on said shaft and spaced from said springs so as to be normally inoperative to actuate said springs when said shaft is rotated, a select nger adapted to be interposed between each of said cams and a corresponding set of contact springsfor rendering the cams operative to actuate their `corresponding contact springs when said shaft is rotated, a plurality of depressible keys, means controlled by said keys during the depression thereof for selectively interposing said select fingers between their respective cams and a corresponding set of contact springs, and means operative when any of said keys is fully depressedfor causing said shaft to rotate.

2. In a call transmitter, the combination of a rotatable shaft, a plurality of cams fixed to said shaft and having mutually peripherally displaced camming areas, a plurality of contact springs disposed relative to said cams and spaced therefrom so as to be inoperativedirectly by the camming areas of said cams when saidshaft is r0- tated, means for selectively rendering said cams operative to actuate said'springs'comprising a select nger for each of said cams, a plurality of depressible keys, means controlled by said keys when depressed for selectively interposing said selectngers between theirrespective cams and said contact springs, whereby said springs are acted, upon `by the camming areas of said cams through said Vselect ngers when said shaft is rotated, and means operative when any of said keys is fully depressed for causing the rotation of 'said shaft. f

3. In a call transmitter, the combination of a rotatable shaft, a pair of identical toothed cams xed to said shaft and arranged thereon so that the teeth of one are peripherally displaced relative to the teeth of the other, a set of contact springs disposed relative to said cams and spaced therefrom so as to be inoperative directly by said cams'when saidshaft is rotated, means for ren dering said cams operative to actuate said springs comprising a select finger for each of said cams, a depressible key, means controlled vby 'said key whendepressed forinterposing said select fingers between their respective 'cams and said contact springs whereby the teeth of said cams alternately operate said contact springs through their respective select fingers when said shaft 'is rotated, and means operative only when said key is fully depressed 'for causing the rotation of said shaft.

l4.. The combination in a call transmitter `of a rotatable shaft, a plurality of cams fixed thereto in spaced relation and having mutually peripherally displaced camming areas, a select finger for each of said cams, a plurality of contact spring sets normally in disengaged association with said cams and each set so located with respect to a pair of said cams as to be operated by the camming areas thereof when one of said select fingers is interposed between its corresponding cam and the associated set of contact springs and said shaft is rotated, control means for each of said select fingers, a plurality of depressible keys for actuating said control means selectively in various combinations whereby a corresponding combination of select fingers are interposed between their corresponding cams and the associated sets of Contact springs when any of said keys is depressed, means controlled during the depression of any of said keys for preparing said shaft for rotation, and means operative only when any of said keys is fully depressed for causing the rotation of said shaft whereby a combination of contact spring operations corresponding to the combination of select fingers .interposed between the contact springs and the corresponding cams is effected.

5. In a call transmitter, the combination of a plurality f depressible keys, contacts, a contact control mechanism comprising a rotatable shaft having fixed thereto a pair of contact operating cams normally dissociated from said contacts and adapted to function successively upon the rotation of said shaft to actuate said contacts, key-operated means, -means controlled by said key-operated means during the depression of any of said keys for preparing said shaft for rotation and for selectively associating said cams with said contacts whereby said contacts are selectively operated by said cams successively when said shaft is rotated, means operative when said key is fully depressed for causing said shaft to rotate, and means comprising a non-linear spring engaged by said key-operated means during the depression 0f said key for restoring said keyoperated means to normal a predetermined interval of time after the full depression of said key.

6. The combination in a signaling system in which a station-selecting signal is characterized by two -successively transmitted signal components, of a line, and a signal transmitter for successively transmitting the signal components over the line 4comprising a plurality of sets of contact springs each of which when operated determines ythe character of a signal component,y

a rotatable shaft, a pair of cams for each set of contact springs mounted on said shaft in inoperative association with the corresponding set of contact springs, the rst cam of each pair corresponding to one portion of a signal transmitting period and the second cam of each pair corresponding to another portion of a signal transmitting period, a plurality of depressible keys, means controlled by said keys during the depression thereof for selecting any combination of a rst and second cam of said pairs of cams and operatively associating them with their corresponding contact springs whereby the selected cams are rendered operable to actuate their corresponding contact springs Vwhen said shaft is rotated, and means operative only when a key is fully depressed for causing the rotation of said shaft, whereupon each of the selected cams functions during its corresponding signaling interval to actuate its corresponding set of contact springs 7. In a call transmitter, the combination of a plurality of sets of contact springs and means for actuating andvreleasing the co-ntact springs of one of said sets and thereafter actuating and releasing the Contact springs of another of said sets comprising a rotatable shaft, a pair of contact spring operating cams `for each set of contact springs carried by said shaft, each pair of cams comprising two identical toothed discs so relatively disposed on said shaft that the teeth of one are peripherally displaced with respect to the teeth of the other whereby one cam of each pair is effective to actuate its corresponding set of contact springs ahead of the other cam when said shaft is rotated, depressible keys, cam-selecting means, means controlled during the depression of certain of said keys for actuating said cam-selecting means to cause them to selectively render a different cam of each pair of cams operable to actuate its corresponding set of. contact springs whereby the selected cams function to operate and release one of said sets of contact springs and to thereafter operate and release another of said sets of contact springs when said shaft is rotated, means responsive to the full depression of any of said keys for causing said shaft to rotate, and means operative independently of said keys after the full depression thereof for causing said cam-selecting means to function for a predetermined interval of time and to thereafter restore said cam-selecting. means to normal.

8. In a call transmitter, the combination of a rotatable shaft, depressible keys, means responsive to the full depression of any of said keys for rotating said'shaft, means for arresting the motion of said shaft after it has been rotated through an arc of predetermined length, contact springs, means for operating and releasing said contact springs during the interval said shaft is rotating through a portion of the said predetermined arc and for reoperating and releasing said contact springs during the interval said shaft is rotating through a subsequent portion of the said predetermined arc comprising a pair of cams carried by said. shaft and consisting of two identical toothed discs so relatively disposed on said shaft thatJ the teeth of one are peripherally displaced with respect to the teeth of the 0 other and are normally inoperative tc actuate said springs when said shaft is rotated, and means controlled during the depression of any of said keys for selectively rendering said ca'ms effective to operate said springs.

FRANCIS 'a rmBBARD. 

